Contemporary designers of golf clubs typically intentionally remove weight from the grips and shafts of clubs. In fact, one golf club manufacturer (Goldwin Golf) currently advertises that it has eliminated 40 grams (about 1.6 ounces) of "dead" weight from the grip end of one of its drivers. This design approach is consistent with the beliefs of many that any additional weight in a club can only retard a club's swing speed at impact, and that any weight not in the clubhead thereby necessarily reduces the maximum amount of momentum that the club can transfer to the ball. Because it is based on the idealization of the swinging of a golf club as a simple pendulum, however, this approach overlooks significant subtleties of the physical dynamics of an efficient golf swing.
Recently, T. P. Jorgensen in The Physics of Golf, (AIP Press, 1994) has modeled the downswing as the motion of a double pendulum driven by a lateral shift of the leading shoulder and a constant torque applied at the leading shoulder (the higher of the double pendulum's two pivot points). He has labeled his model as a "Standard Model" of the downswing. Further consideration of this model and of its implications for the optimal weighting of golf clubs is discussed in the section herein entitled "Operation."
For more than 50 years, makers of golf clubs have referred to clubs with a higher percentage of their overall weight concentrated in their heads as having greater so-called "swingweight". Strictly speaking, swingweight is a measure of a club's moment of weight about an arbitrary axis, with the axis being located either 14 inches (Lorhythmic Scale, Prorhythmic Scale, et al) or 12 inches (Official Scale) from the butt end of the shaft. On the Lorythmic Scale, one unit of swingweight, which is smaller than any difference that a golfer can feel between two clubs, is roughly equivalent to about 0.065 ounces in the head of a wood or about 0.07 ounces in the head of an iron. Historically, the Official Scale is a revision of the Lorhythmic Scale, which appears to have been chosen, in part, to facilitate the design of a relatively compact device for measuring a moment of weight of golf clubs.
Neither of these scales accurately measures a club's moment of weight about the club's wrist cock axis, which is the axis about which the club actually rotates relative to the leading arm during a swing. In practice, when a golfer grips a club with both hands, the wrist cock axis is located in the vicinity of a righty's left thumb or a lefty's right thumb. Either way, when a golfer grips a club at its full length, we conventionally assume that the wrist cock axis is located about 5 inches from the butt end of the shaft.
In spite of swingweights not being measured relative to the wrist cock axis, however, golf club makers continue to use swingweight as a basis for matching sets of clubs. These matched sets normally progress in even increments of length and weight from longer clubs with lighter heads to shorter clubs with heavier heads. Consequently, a constant swingweight can be maintained by choosing an appropriate common increment in clubhead weight to offset the combined effects of shafts with incrementally decreasing lengths and weights and grips with constant weight.
The traditional method of matching by swingweight also produces sets of clubs for which each club's center of gravity gets closer to the head end of its shaft for successively shorter and heavier clubs. This fact is especially relevant because other inventors previously have patented a variety of non-traditional methods of matching sets of clubs by altering the weights of one or more of the clubs' components. To this inventor's knowledge, however, none of these methods produce sets of clubs for which the centers of gravity do not get closer to the head ends of the shafts for at least some of the clubs in a matched set as the clubs get successively shorter and heavier.
For example, U.S. Pat. No. 4,887,815 to Hughes et al. describes that various weights may be removed from conventional clubheads when counterweights of constant weight are added to produce a set of clubs with significantly reduced but roughly constant swingweights. U.S. Pat. No. 5,152,527 to Mather et al. describes that various weights may be removed from the clubheads, and counterweights of decreasing weight are added to shafts of decreasing length. In U.S. Pat. No. 5,228,688 to Davis it is discussed that conventional lengths and faces of clubs are varied, and counterweights of decreasing weight are added to clubs of decreasing length. In U.S. Pat. No. 4,461,479 to Mitchell, the counterweights for woods are substantial, with those for the 3, 4, and 5-wood in an example exceeding those for any of the irons. The counterweights for successive irons in this same example also progress by too small a common increment (0.10 ounce=2.853 grams) to prevent the centers of gravity of successively shorter clubs from moving progressively closer to the head ends of their shafts.
Considering, next, devices for damping unwanted vibrations of the shafts of golf clubs, we observe that one major shaft manufacturer (True-Temper) recently has introduced shafts with energy-absorbing inserts or liners called SENSICORE.TM., and a major club manufacturer (Karsten Manufacturing or "Ping") has introduced another vibration-dampening mid-shaft insert known as CUSHIN.RTM.. Both of these vibration-damping mechanisms are relatively light in weight and are positioned in the shafts of clubs below the grips.
In U.S. Pat. No. 5,362,046 to Sims it is disclosed that a vibration-damping device is inserted in the butt end of the shafts of clubs. This device, an embodiment of which currently is being marketed as SIMS SHOCK RELIEF.TM., necessarily incorporates a member that is relatively free to move within the shaft. As disclosed, this device is composed entirely of an elastomer, and the ratio of its head width to its stem length is in the range of 5:1 to 1:1. Thus, it is light in weight, and, except for its vibration damping, has little effect on a club's dynamic response.
The known prior art makes no attempt to design or to use counterweights simultaneously as frictionally dissipative, vibration-damping devices (dash pots) in any of the counterweight devices and systems cited above. Indeed, special care has been taken in all of the patents to affix the counterweights immovably to the interior of shafts. In U.S. Pat. No. 4,461,479 to Mitchell, for example, counterweights are encased tightly in flexible sleeves that, in turn, are bound tightly within clubs' hollow shafts in an effort to insulate the counterweights from mechanical stresses, such as vibrations of the shafts.
Accordingly, a need yet remains for golf clubs and for complete sets of golf clubs with improved overall playability and instructional utility, and which damp or lessen vibration and shock in the user's hands. The present invention is directed principally to the provision of such clubs and sets of clubs.